Low impact ball-seat apparatus and method

ABSTRACT

An apparatus for restricting fluid flow includes: a ball receiving element disposed in a first fluid conduit and configured to receive a ball that has been advanced through the first fluid conduit and at least partially restrict a fluid flow in the first fluid conduit; and at least one second fluid conduit in fluid communication with the first fluid conduit at an upstream location relative to the ball receiving element, the at least one second fluid conduit configured to divert a portion of the fluid from the first fluid conduit and reduce an impact between the ball and the ball receiving element.

BACKGROUND

In the drilling and completion industry and for example in hydrocarbon exploration and recovery operations, a variety of components and tools are lowered into a borehole for various operations such as production operations, for example. Some downhole tools utilize ball-seat assemblies to act as a valve or actuator. Ball-seat assemblies are used with, for example, hydraulic disconnects, circulating subs and inflatable packers.

Actuation of a ball-seat assembly generally includes releasing a ball or other plug into a fluid conduit and allowing the ball to drop onto the ball seat and restrict a fluid flow therein. The impact between the ball and the ball seat can produce pressure waves, which can cause wear and/or damage to components of the assembly. For example, in subterranean operations, oil and other downhole fluids can be pumped at a rate of up to 80 oil barrels per minute (bbl/min). Such fluid rates can cause the ball to transfer a large amount of momentum onto the ball seat, which can cause fracture or deformation in the ball seat and other components.

SUMMARY

An apparatus for restricting fluid flow includes: a ball receiving element disposed in a first fluid conduit and configured to receive a ball that has been advanced through the first fluid conduit and at least partially restrict a fluid flow in the first fluid conduit; and at least one second fluid conduit in fluid communication with the first fluid conduit at an upstream location relative to the ball receiving element, the at least one second fluid conduit configured to divert a portion of the fluid from the first fluid conduit and reduce an impact between the ball and the ball receiving element.

A method of restricting fluid flow includes: releasing a ball into the first fluid conduit, the first fluid conduit having a fluid flow therein; receiving the ball in a ball receiving element disposed at the first fluid conduit and at least partially restricting the fluid flow; and diverting a portion of the fluid from the first fluid conduit at an upstream location relative to the ball receiving element via a second fluid conduit to reduce an impact between the ball and the ball receiving element.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 is a cross-sectional view of an embodiment of a ball-seat assembly;

FIG. 2 is a partial cross-sectional view of the ball-seat assembly of FIG. 1 including a second fluid conduit; and

FIG. 3 is a flow diagram depicting a method of restricting fluid flow in a conduit.

DETAILED DESCRIPTION

The apparatuses, systems and methods described herein provide for the mitigation of pressure waves and other loads caused by actuation of a ball-seat assembly. A downhole assembly includes a first fluid conduit having a longitudinal component to guide a ball released into the conduit to a receiving element such as a ball seat. A second fluid conduit such as a bypass conduit is provided in fluid communication with the fluid conduit and is configured to divert a portion of the fluid in the fluid conduit. The bypass conduit reduces the fluid velocity in the fluid that carriers the ball to the ball seat during actuation. As a result, the severity of impact between the ball and the ball seat is reduced. This reduction decreases the potential for damage to the downhole assembly and also mitigates pressure waves produced by the impact and reduces damage and/or wear on downhole components such as the ball and the ball seat.

Referring to FIG. 1, a downhole tool 10, such as a ball seat sub, configured to be disposed in a borehole 11, includes a housing 12 having a longitudinal bore or fluid conduit 14. A ball-seat assembly includes a ball receiving element such as a ball seat 16 included in the conduit 14 to retain a ball 18 that is released from a releasable support element or releasing mechanism 20 in the housing 12. In one embodiment, the ball 18 is a spherical metal or plastic plug, although “ball” may refer to any type of moveable or droppable plugging element, such as a drop plug, and may take any desired size or shape, such as a cone or cylinder. Actuation of the ball seat assembly includes releasing the ball into the fluid conduit 14, for example by dropping the ball 18 into and/or pumping the ball 18 through the fluid conduit 14 from a surface or downhole location. The ball 18 falls and/or is advanced by downhole fluid toward the ball seat 16 and is seated on the ball seat 16 to restrict fluid flow through the conduit 14.

The ball seat 16 may be an annular component connected to the conduit 14, or any other device or configuration providing a restriction in the diameter or cross-sectional area of the conduit 14 sufficient to prevent the ball 18 from passing therethrough. In one embodiment, the ball seat 16 is directly disposed on and/or attached to the inner surface of the conduit 14 or is formed from a reduced diameter portion of the conduit 14. In one embodiment, the ball seat is disposed on or is part of a movable component such as a piston or a sliding sleeve 20 for use, for example, as an actuator or valve.

The tool 10 includes at least one cavity or second conduit, such as a bypass conduit 22, connected in fluid communication to the fluid conduit 14 and a primary fluid flow 24 at a location above and/or upstream of the ball seat 16. The bypass conduit 22 or other cavity diverts a portion of the primary fluid flow 24 (i.e., a secondary fluid flow 26) and may be configured to cause the secondary fluid flow 26 to circumvent the ball seat 16.

The bypass conduit(s) 22 is configured to produce a secondary fluid flow rate or velocity that reduces the primary fluid flow rate or velocity around the ball seat 16 by a selected amount. In one embodiment, the cross-sectional flow area of the bypass conduit 22 is selected to reduce the primary fluid flow rate. In one embodiment, the bypass conduit 22 acts to reduce the primary fluid flow rate, and the resulting impact of the ball 18, in an amount that is proportional to ratio of the cross sectional flow area of the fluid conduit 14 (the primary flow channel) to the total cross sectional flow area of the bypass conduit(s) 22. The bypass conduit 22 or cavity shape, cross-sectional area and/or diameter can be designed so as to generate a known or desired parallel impedance or parallel hydraulic resistance. In addition, the secondary fluid flow rate may be controlled via one or more regions of reduced cross-sectional area and/or bends in the bypass conduit 22. The flow impedance can be designed by varying channel diameter, number of bends, series of valves or a combination of these. In one embodiment, one or more flow control valves 28 are included in fluid communication with the bypass conduit 22 to control the secondary fluid flow rate and/or stop the secondary fluid flow.

Fluid partitioning into the bypass conduit 22 or other secondary fluid cavity provides pressure relief in the main fluid conduit flow. The reduced borehole flow pressure is still enough to cause ball-seat actuation but drastically reduces the pressure surge on the ball seat assembly upon impact. This directly reduces the material and/or design failure propensity upon ball impact onto the ball seat 16. In one embodiment, the bypass conduit 22 is configured so that the primary fluid flow rate in the ball seat area is reduced to a minimum level required to cause the ball 18 to contact the ball seat 16 and maintain contact with the ball seat 16.

In one embodiment, the bypass conduit 22 includes an inlet 30 disposed at a location upstream of the ball seat 16. In one embodiment, the inlet 30 is located proximate to the sliding sleeve 20 or other moveable component and/or the ball seat 16. In one embodiment, the bypass conduit 22 extends to an outlet 32 into the fluid conduit at a location downstream of the ball seat 16. In this way, the bypass conduit 22 may create a fluid communication between the upstream and downstream side of the ball seat 16.

In one embodiment, the ball seat 16 is attached to or otherwise fixedly disposed relative to the sliding sleeve 20 or other moveable component. In this embodiment, the primary fluid flow 24 is partitioned and only a part of it is used to actuate the sleeve 20. The remainder flow, i.e., the secondary fluid flow 26, is diverted downstream of the ball seat 16, bypassing the ball seat area directly.

The downhole tool 10 is not limited to that described herein. The downhole tool 10 may include any tool, carrier or component that includes a ball seat assembly. The carriers described herein, such as a production string and a screen, are not limited to the specific embodiments disclosed herein. A “carrier” as described herein means any device, device component, combination of devices, media and/or member that may be used to convey, house, support or otherwise facilitate the use of another device, device component, combination of devices, media and/or member. Exemplary non-limiting carriers include borehole strings of the coiled tube type, of the jointed pipe type and any combination or portion thereof. Other carrier examples include casing pipes, wirelines, wireline sondes, slickline sondes, drop shots, downhole subs, bottom-hole assemblies, and drill strings. In addition, the downhole tool 10 is not limited to components configured for downhole use.

FIG. 3 illustrates a method 40 of restricting fluid flow in a component. The method includes, for example, actuating a valve or packer in a downhole assembly. The method 40 includes one or more stages 41-43. Although the method is described in conjunction with the tool 10, the method can be utilized in conjunction with any device or system (configured for downhole or surface use) that utilizes a ball-seat assembly.

In the first stage 41, in one embodiment, the tool 10 is disposed at a downhole location, via for example a borehole string or wireline. In the second stage 42, the ball-seat assembly is actuated by releasing the ball 18 into the conduit 14, for example by dropping the ball 18 into the conduit 14 and/or pumping the ball 18 through the conduit 14. The primary fluid flow 24 is used to actuate the ball seat assembly and advance the ball 18. The ball 18 advances through the conduit 14 and impacts the ball seat 16. In the third stage 43, a portion of the primary fluid flow 24 is diverted as the secondary fluid flow 26 to the bypass conduit 22 to reduce the impact between the ball 18 and the ball seat 16. The magnitude of the impact pressure of the ball 18 onto the ball seat 16 is reduced and can be controlled via partitioning the fluid flow to circumvent the seat. For example, a magnitude of the secondary fluid flow 24 can be reduced by a desired amount by changing the diameter of the bypass conduit 22 or otherwise changing the flow area of the bypass conduit. Various valves 28 or other fluid flow control mechanism may also be used to control the secondary fluid flow rate. In one embodiment, the secondary fluid flow 24 returns to the fluid conduit 14 at a location downstream of the ball seat 16.

In one embodiment, the method 40 includes actuating a moveable component such as the sliding sleeve 20 by the impact. In this embodiment, fluid is diverted and returned to the main fluid conduit 14 downstream of the ball seat 16.

In one embodiment, the ball seat 16 is fixedly disposed relative to the conduit 14, and fluid is diverted via the bypass conduit 22. In one example, a restricting mechanism such as a valve 28 may be operated or actuated to close off the bypass conduit 22 so that no fluid is introduced downstream after the ball 18 is seated on the ball seat 16. Actuation of the valve 28 can be coordinated with release of the ball 18, so that the valve 28 is closed at or near the same time that the ball 18 is seated. This may be accomplished by, for example, a processor in operable communication with the release mechanism 20 and the valve 28. For example, the processor can determine the time after release, based on the fluid flow rates in the main fluid conduit 14 and/or the bypass conduit 22, that the ball 18 impacts the ball seat 16. The processor may then close the valve 28 at or near the ball impact time so that the ball seat assembly can completely close off the conduit 14.

The systems and methods described herein provide various advantages over existing processing methods and devices. Ball-seat structure loads include both solid-to-solid contact pressure due to ball momentum, and pressure waves including compressive pressure waves (shown as “Pwh” in FIG. 2) on the upstream face of the ball seat assembly and tensile waves (shown as “−Pwh” in FIG. 2) on the downstream face. The apparatuses and methods described herein act to reduce fluid flow and ball velocity that reduces the loads. Thus, damage to the ball seat assembly and other components due to impact and pressure waves can be reduced. The reduction in ball-seat load can enable the use of a wider range of construction materials and reduce the complexity of ball-seat design, for example by reducing the need for relatively complex ball seat designs to reduce impact. In addition, the apparatuses can allow for the ball seat to have a larger inner diameter due to the reduced contact stress.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated by those skilled in the art to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention. 

1. An apparatus for restricting fluid flow, comprising: a ball receiving element disposed in a first fluid conduit and configured to receive a ball that has been advanced through the first fluid conduit and at least partially restrict a fluid flow in the first conduit; and at least one second fluid conduit in fluid communication with the first fluid conduit at an upstream location relative to the ball receiving element, the at least one second fluid conduit configured to divert a portion of the fluid from the first fluid conduit and reduce an impact between the ball and the ball receiving element.
 2. The apparatus of claim 1, further comprising a carrier including the fluid conduit and configured to be disposed in a borehole.
 3. The apparatus of claim 1, wherein the upstream location is proximate to the ball receiving element.
 4. The apparatus of claim 1, wherein the diverted portion causes a fluid flow rate in the first fluid conduit to be reduced.
 5. The apparatus of claim 1, wherein the ball receiving element is attached to a moveable component, the moveable component configured to move relative to the first fluid conduit in response to the impact.
 6. The apparatus of claim 1, wherein the moveable component is selected from at least one of a sliding sleeve and a piston.
 7. The apparatus of claim 1, wherein the at least one second fluid conduit is configured to return the diverted portion of the fluid to the fluid conduit at a downstream location relative to the ball receiving element.
 8. The apparatus of claim 1, wherein the second fluid conduit includes at least one mechanism configured to restrict fluid flow within the second fluid conduit.
 9. The apparatus of claim 8, wherein the at least one mechanism includes at least one of a valve, a bend in the second fluid conduit and a restriction in a cross-sectional area of the conduit.
 10. The apparatus of claim 1, further comprising a housing including the fluid conduit therein.
 11. The apparatus of claim 10, wherein the second fluid conduit is formed within a wall of the housing.
 12. A method of restricting fluid flow, comprising: releasing a ball into the first fluid conduit, the first fluid conduit having a fluid flow therein; receiving the ball in a ball receiving element disposed at the first fluid conduit and at least partially restricting fluid flow; and diverting a portion of the fluid from the first fluid conduit at an upstream location relative to the ball receiving element via a second fluid conduit to reduce an impact between the ball and the ball receiving element.
 13. The method of claim 12, further comprising disposing a carrier in a borehole, the carrier configured to include the ball receiving element and the first fluid conduit therein.
 14. The method of claim 12, wherein the upstream location is proximate to the ball seat.
 15. The method of claim 12, wherein diverting the portion of the fluid causes a fluid flow rate in the first fluid conduit to be reduced.
 16. The method of claim 12, wherein the ball receiving element is attached to a moveable component, the moveable component configured to move relative to the first fluid conduit in response to the impact.
 17. The method of claim 12, further comprising returning the diverted portion of the fluid to the fluid conduit at a downstream location relative to the ball receiving element.
 18. The method of claim 12, wherein diverting includes controlling a diverted fluid flow rate within the second fluid conduit to control the fluid flow rate in the first conduit between at least the upstream location and the ball receiving element.
 19. The method of claim 18, wherein the diverted fluid flow rate is controlled by at least one of a valve, a bend in the second fluid conduit and a restriction in a cross-sectional area of the second fluid conduit.
 20. The method of claim 12, wherein the second fluid conduit is formed within a wall of a housing that includes the first fluid conduit. 